feat(linear_algebra/affine_space): more lemmas (#3615)
Add further lemmas on affine spaces. This is the last piece of
preparation needed on the affine space side for my definitions of
`circumcenter` and `circumradius` for a simplex in a Euclidean affine
space.
Co-authored-by: Vierkantor <Vierkantor@users.noreply.github.com>
